IMAP migration in 8.0.2

Hi.
I'm installing a fresh 8.0.2 and was wondering if I could benefit from the import tools available in admin console, as I have to migrate existing users from an IMAP server.
In the past I successfully used imapsync, but now I see I can do that from Zimbra directly, but I couldn't find documentation about how it works. I see I can pick users and config from an XML file, but how should it be formatted?
Also, if I run import now and then rerun the import next week, will it check for existing emails or will it generate duplicates? Imapsync used to care about it, copying over just new emails.

I checked online and directly into zimbra admin but couldn't find documentation about that. If anyone can point me to updated info, it would be great!